Summary
Background
Conventional coronary angiography (CA) is still recommended before valvular surgery. Preliminary studies suggest that multislice spiral computed tomography coronary angiography (MSCT-CA) can be used to rule out coronary artery disease (CAD).
Aim
To assess prospectively the safety of ruling out CAD before surgery solely on the basis of normal MSCT-CA in patients with severe aortic valve disease.
Methods
We included all consecutive patients scheduled for aortic valve surgery. We first estimated the calcium score (Agatston score equivalent [ASE]). Patients underwent injected MSCT if the ASE was < 1000. CA was cancelled when MSCT-CA quality was sufficient and showed no significant CAD. Our primary endpoint was the occurrence of perioperative myocardial infarction in patients who underwent surgery with no prior CA.
Results
Between 1st July 2005 and 30th June 2008, we included 199 patients with severe aortic valve disease: 118 men (59%); mean age 69 ± 12 years; 63 patients (32%) underwent CA directly because the ASE was ≥ 1000. Of 136 patients who underwent MSCT-CA, 106 (78%) had a normal MSCT-CA and underwent aortic valve surgery without prior CA; CA was performed in 30 patients because of abnormal ( n = 18) or bad quality ( n = 12) MSCT-CA. One patient of the 106 (0.94%, 95% confidence interval 0.17–5.15) had a perioperative myocardial infarction.
Conclusions
When the ASE is < 1000, MSCT is safe and may be recommended instead of CA as a first-line means of ruling out CAD in patients with severe aortic valve disease.
Résumé
Préambule
Une coronarographie est généralement réalisée avant une chirurgie valvulaire. Des études préliminaires, prenant la coronarographie comme référence, ont suggérées que le scanner coronaire pouvait exclure une coronaropathie. Nous avons évalué de manière prospective la sécurité de l’exclure sur la seule base d’un scanner normal avant chirurgie valvulaire aortique.
Méthode
Inclusion des patients consécutifs programmés pour une chirurgie de la valve aortique. Premièrement, estimation du score calcique selon la méthode d’Agatston. Les patients ne bénéficiaient du scanner injecté que lorsque le score calcique était inférieur à 1000. La coronarographie était annulée quand le scanner était de bonne qualité et permettait d’exclure une coronaropathie significative. Le critère primaire était la survenue périopératoire d’un IDM chez les patients n’ayant pas subi de coronarographie.
Résultats
Entre juillet 2005 et juin 2008, nous avons inclus 199 patients avec valvulopathie aortique sévère : hommes, 118 (59 %) ; âge = 69 ± 12 ans ; 63 patients ont subi la coronarographie d’emblée en raison d’un score calcique supérieur ou égal à 1000. Sur les 136 ayant bénéficié du scanner avec injection, 106 (78 %) avaient des coronaires saines et ont été opérés sans coronarographie préalable, alors qu’une coronarographie a du être réalisée chez 30 patients pour anomalies au scanner ( n = 18) ou mauvaise qualité ( n = 12). Un seul patient sur 106 a présenté un IDM périopératoire (0,94 %, IC 95 % [0,17–5,15]).
Conclusion
Quand le score calcique est inférieur à 1000, le scanner coronaire est sûr et pourrait être recommandé en première intention avant la coronarographie chez les patients porteurs d’une valvulopathie aortique sévère.
Background
In all forms of valvular heart disease, significant associated CAD worsens the perioperative prognosis. CA is still recommended in the preoperative assessment of patients with valvular heart disease (Grade 1 American College of Cardiology/American Heart Association guidelines 1998 and 1999; Grade 1 European Society of Cardiology 2007 ), although no large-scale clinical trial has assessed the contribution of this invasive investigation. We published a preliminary study that suggested that MSCT-CA might serve as an alternative to invasive coronary angiography in patients scheduled for aortic valve replacement. MSCT-CA was compared with conventional CA. In patients with a calcium score of < 1000, the sensitivity of the MSCT-CA in detecting significant stenosis was 100% and its specificity was 80%. The positive and negative predictive values were 55 and 100%, respectively. The objective of the present study was to assess prospectively the perioperative myocardial ischaemic outcome of patients undergoing valve surgery, after ruling out significant CAD solely on the basis of a normal MSCT-CA result.
Methods
This was a single-centre, prospective, diagnostic, management outcome study. The institutional review board approved the study and all patients provided written informed consent.
From 1st July 2005 to 30th June 2008, all consecutive patients aged 18 years and over who were referred to our cardiology department for CA in the preoperative assessment of aortic valve disease (stenosis or regurgitation) were considered for inclusion. Exclusion criteria were: irregular heart rate; iodinated contrast agent contraindication; renal insufficiency; and already rejected for valve surgery for non-CAD reasons.
Our main objective was to validate prospectively the ruling out of significant CAD on the basis of a normal or subnormal MSCT-CA result.
We assumed that patients with a normal or subnormal coronary artery network have a perioperative risk of an ischaemic cardiac event of approximately 1% ; in a preliminary study , we detected “normal” patients with a negative predictive value of 100% compared with CA; in the same study, we found that CA could have been avoided in 35/55 cases.
Therefore, 110 patients with a normal MSCT-CA were needed, given the hypothesis that none or one of them (approximately 1%) would present with a cardiac ischaemic event during the perioperative period, allowing us to obtain an upper limit of the 95% confidence interval (CI) of < 5% for the risk of an ischaemic event (Euro Heart Survey) . In accordance with our previous data to obtain 110 patients with a calcium score < 1000 and a normal or subnormal MSCT-CA we planned to include 205 patients.
Except for MSCT-CA and (possibly) CA, clinicians in charge of the patient were allowed to perform any other preoperative evaluation. They made the decision to schedule surgery or reject the patients. Patients not operated on within 6 months after the initial evaluation (including preoperative MSCT-CA) were excluded from the analysis.
MSCT protocol and image reconstruction
The MSCT data sets were acquired using a 16-slice MSCT (Philips Mx8000 IDT 16, Eindhoven, The Netherlands). Briefly, a native scan without contrast medium was performed to determine total coronary calcium. A calcified lesion was defined as an area of > 3 connected pixels, > 130 Hounsfield units, and was expressed as ASE. On the basis of previously published data , we determined that in this particular population, contrast medium injection was useless when the ASE was > 1000.
Next, a volume data set was acquired (16 × 0.75 mm cross-section; gantry rotation time, 420 ms; table feed, 2.8 mm per rotation), covering the distance from the carina to the diaphragmatic side of the heart. The entire heart was scanned during a single breath-hold; 80–120 mL of contrast agent (Iomeron 350, Bracco SA, Milano, Italy) was injected continuously at a rate of 4 mL/s. Automated detection of peak enhancement in the aortic root was used to time the scan.
Cross-sectional images were reconstructed with a slice thickness of 0.8 mm at 0.4 mm intervals with retrospective gating. A scoring method analogous to the Agatston score was used to quantify coronary calcium.
All data sets were analysed independently by two physicians experienced in MSCT, using multiplanar reformations, three-dimensional reconstructions by the “volume rendering” technique and “comprehensive cardiac” software. They were asked to give a consensus on the presence of significant CAD on a per patient basis. Image quality was classified as “good” (no or only minor motion artefacts), “moderate” (substantial motion artefacts), or “bad” (significant motion artefacts and/or low signal-to-noise ratio and no luminal assessment of significant stenosis possible in at least one vessel). In addition, the observers were asked to state their recommendations for patient management (i.e., CA indicated or not).
CA was performed when recommended on the same day after MSCT if the ASE was > 1000, and 2 days later if the MSCT was of bad quality or if significant CAD was suspected. Angiograms were evaluated by an independent observer, blinded to the MSCT-CA results, using quantitative CA (Numeric System, DX-DLX, General Electric Medical Systems, Buc, France) as the gold standard of stenosis detection. Lesions with a ≥ 50% diameter reduction counted as significant stenosis.
Follow-up
All patients were followed for 30 days after aortic valve surgery. Perioperative myocardial infarction was defined as a significant elevation (≥ 20 ng/mL) of plasma troponin Ic during the first 24 hours after surgery and no other clear explanation. During the postsurgery period, myocardial infarction was defined by the association of chest pain, new onset Q waves and troponin Ic elevation (≥ 0.2 ng/mL above the last measurement) . The outcome events were judged by an adjudication committee, comprising three independent experts who were blinded to the tests performed before surgery. In cases of death or suspected myocardial infarction within the 30-day period, the patient chart was reviewed, and death and troponin elevation were judged as being related or unrelated to a coronary artery ischaemic event. Unrelated events were due to obvious perioperative causes, such as a drawback in myocardial protection (isolated troponin Ic elevation with no Q waves and no wall-motion abnormality).
Statistical analysis
General characteristics, CAD risk factors and clinical signs were expressed as means and standard deviations for continuous variables and as percentages for qualitative variables. The rates of myocardial infarction and death during follow-up in patients undergoing aortic valve surgery with no prior CA on the basis of a normal MSCT-CA were assessed with their respective 95% CIs. All analyses used SPSS analysis software, version 12.0 (SPSS Inc., Chicago, IL, USA).
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